Make hsm.getVolumesList() pool independent.

Related to BZ#960952.

Change-Id: Ib810ca24818fa4a77905032694a05c0d86ef75e2
Signed-off-by: Eduardo <ewarszaw@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/15766
Reviewed-by: Ayal Baron <abaron@redhat.com>